A certain amount of vibration or shock occurs naturally as a dynamic load in an aircraft engine system. In a “hard mount” engine mount system, the vibration or shock is transmitted through the metal, which provides very little vibration isolation, to the aircraft frame. In order to foster a smoother flying experience, traditional aircraft design generally incorporates isolators in the engine mount system. Isolators provide vibration isolation with damping and it has lower mount stiffness than a ‘hard mount’ configuration. Owing to lower stiffness of isolators, the relative deflection at mount is higher than ‘hard mounted’ configuration for same transmitted load. To limit the relative deflection at isolator mount under high mount load conditions, snub clearance is provided. Snub clearance is a clearance in the isolator wall beyond which if relative motion occurs, a metal to metal contact will happen which will then reduce any further relative motion. In normal course of operation, relative motion at mount rarely exceeds snub clearance.
In extreme loading conditions, such as a fan blade out event (loss of a fan blade), crash landing, or extreme maneuver loading conditions, high relative displacement in the engine mount is developed. The relative motion at the mount under these loading conditions is often greater than the snub clearance, and a brief metal-to-metal contact occurs in the isolator. The mount load during metal-to-metal contact in the isolator is quite high in magnitude, and referred to as a “high transient mount load;” the metal-to-metal contact is referred to as “snubbing.” When snubbing happens, there is momentary increase in transmitted mount load. Mount load due to the snubbing phenomenon is problematic because its magnitude is often significantly greater than the mount load without snubbing and may be higher than what is experienced by a hard mounted engine.
Accordingly, it would be desirable to reduce the high transient mount load in an aircraft engine mounting system. A desired improvement reduces the impact of the snubbing phenomenon without adding to the weight or space claim of the engine mounting system.